There are image-reading devices known in the art that match the distance from the image-reading unit to the reference member that is related to shading correction to the distance from the image-reading unit to the read position that is related to image reading. Specifically, the reference member is mounted over the read position during shading correction and removed from the read position when reading an image from an original. Alternatively, the reference member is moved to the read position during shading correction and retracted from the read position during image reading.